Glass



Feb. l1, 1936. L. NAvlAs 2,030,390

GLASS Filed Aug. ll, 1934 IYwentof: vLOLJUS Nava,

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Patented Feb. ,11, 1936y ci:A A

GLASS Louis Navias, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application August 11, 1934; serial No. 739,455

z claim. (ci. 11s- 122) The present invention relates to the glass art and its object is to produce a glass which is resistant chemically and physically to the decomposing and disintegrating eiIect of highly vheated metallic vapors. In particular it is the object of my invention to provide a glass suitable for use as a protective coating or glaze upon the interior surface of sodium lamp bulbs, where the glaze is exposed to highly heated and therefore chemically active sodium vapor.

It has been proposed heretofore to coat glass containers which are not inert to hot alkali vapor with a borate which is substantially devoid of silica. Such borates are not resistant to moisture and weathering influence and tend to deteriorate before the bulb is sealed' during the course of manufacture. Glasses containing silica in addition to boric oxide, and commonly termed borosilicates, have been found better suited for this 20 purpose. In accordance with my present invention I have provided new and improved borosilicate glasses which'are moisture-resistant while.

also being more inert chemically to hot sodium vapor and also are more transparent than the borosilicate glasses which have heretofore been employed.

In glasses embodying my invention the content of boric anhydride (B203) within the limits of about to 50% and the content of silica (S102) 3 less than'about 20% and preferably within the limits of about 1/2 to .15% make up the baseforming constituents which include barium oxide within the limits of about 'to 50%.

The accompanying drawing lshows in Fig. l a vapor lamp embodying my invention and in Fig. 2 is shown an enlarged detail view of a sectionfof a portion of the glass wall. As illustrative of my invention is a glass containing the following con stituents: Example! Parts Sodium oxide (Na20) l1 Aluminlmi oxide (A1203) e 10 Barium oxide (BaO) 31 46 Boron oxide (B202) 40 Silica (S102) 8 56 varied within the limits above indicated providing a proper relation is maintained between the basic -and acid constituents to produce a glass, having a desired coeillcient o1' expansion and other desired physical characteristics.

`For example, a glass also suitable for use as a 5 protective glaze upon the interior of lime glass bulbs may have the following analysis:

ErampleZ 'Parts lo Sodium oxide (Na20) 11 Aluminum oxide (Al200).. r 11 Barium oxide (BaO) 33 Boron oxide (B202) 42 silica (sioi) 3 l5 The lamp shown in Fig. 1 comprises an elongated glass container I at the opposite ends of which are located electrodes 2, 3, between which an arc discharge operates through the gaseous contents of the container. This lamp is of the type 20 shown in copending application Serial No. 642,882, lfiled November 16, 1932, by Andrew H. Young (see corresponding British Patent 405,232) 'I'he particular electrodes here shown consist of a coiled lamentary member f, which ordinarily consists 25 of nickel coated with barium oxide, or other thermionicallyy active material, and a surrounding v cylindrical member c which also may consist of nickel (see electrode 2) and which is connected to the member f. The filamentary member f is 3o supplied with heating current by the leading-in conductors l, E, which are sealed into the glass envelope as usual and are surrounded by protective sleeves 'C of refractory material. The electrode 3 is similarly connected to conductors 1, 35 0 (also surrounded by a refractory sleeve) which are kept from unduly vibrating by an anchor S engaging with the glass container. The sealing region of the envelope adjacent the stem Il is shut oil from the vapor space by a partition II. '40 'Ihe container ilrst is evacuated during fabrication of the lamp, then is charged with luminosityproducing vapor, such as sodium for example, as indicated at I2. Other vaporizable materials such as potassium, cadmium, zinc, and the like, may be 45 used in such lamps. The sodium, or the like, may be introducedv from a small glass capsule I3 which is broken when the material therein is to be releasedrl A gas, such as neon, or argon, also may be present, usually at a pressure of two or three millimeters of mercury. l

As shown in Fig. 2, the inner surface of the glass envelope I is lined with a glass or glaze I4 which is resistant to the disintegrating eiiect of the alkali vapor, or whatever gaseous filling may l be employed. The thickness of the glaze may be even less than shown in Fig. .2.

The preparation of a glass having an analysis .within the limits indicated above is within the knowledge of the ordinary glass maker. However, for the purpose of illustration there is given below the composition of a batch oi raw glassforming materials which would yield by fusion (preferably in a platinum crucible) a glass having a composition within the limits characteristic of my invention. A batch yielding a glass having analysis corresponding to Example 1 may consist oi the following ingredients:

Sodium carbonate (hydrated) 14.0 Sodium nitrate 11.0 Aluminum oxide 10.0 Barium carbonate 39.9 Boric acid '11.1 Quartz or other form of silica 8.0

` When the fusin is complete the platinum cru- ,cible-may be quickly cooled to cause separation of the contents from the chilled walls of the crucible. The glass thusA produced is crushed and ground while being kept free from moisture. The pow-,r

dered product preferably is stored until desired for use in a space maintained at a temperature above 100" C. It may be applied to the inner surface of a lamp bulb such as shown in the drawing while suspended in an organic liquid which is evaporated after the nlm has been applied. The

"content of which is within the limits of about 25 'to 50 per cent, the boric anhydride of which is within the limits oi 50 to 20 per cent, and the silica content of which is less than about 20 per cent.

2. In combination with im cieca-ical discharge device which contains a quantity of chemicallyl active material and comprising a container which is susceptible to chemical attack by said material, a lining for said container comprising a bariumcontaining yborosilicate glass, containing the tol# lowing ingredients in the proportions indicated:

-Parts' Sodium oxide (NazO) 1l Aluminum Oxide (A1201) 10 Barium Oxide (B30) v31 Boron oxide (B203) Q... 4i!) Silica (SiO2)--.. 8

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